问题
选择题
Some of the rubbish, such as food, paper and iron, _____ away over a long period of time.
A．rot
B．rots
C．is rotting
D．are rotted
答案
答案：B
句子的主干是：Some of the rubbish _____ away over a long period of time. rubbish是不可数名词,谓语动词用单数.